There’s been a lot written about the Raspberry Pi, a small single-board computer with I/O pins on the circuit board, and a small price tag (£25 or so). For me, the most exciting aspect of the Raspberry Pi is the fact that it has lots of methods of input and output of digital signals to and from the board.

Here’s a little tip for anyone with an Oil Watchman tank guage. If your batteries run out, you don’t need to spend £30 or so replacing it. You can open the tube and replace the four AAA cells that are inside, it’s a simple five minute job.